This proposal will study the effects of lung denervation on the structure and function of the airways by testing two general hypotheses: a.increased airway strain during breathing initiates a fibroproliferative response in denervated airways and b. neurotrophins produced by denervated neuronal targets modify neuropeptide gene expression in airway parasympathetic ganglia. The experimental approach will pursue two specific aim. The first aim will be to define the effects of denervation on the transciptional regulation of type I procollagen in rats. Accordingly, procollagen expression will be assessed by i situ hybridization after unilateral lung vagotomy or syngeneic lung transplantation. Differences in procollagen mRNA levels between denervated and control lungs will be: 1. examined after experimental manipulations of airway strain and 2. related to the expression of two growth factors which contain strain- responsive elements in their gene promoter and may up-regulate collagen transcription: platelet-derived growth factor (PDGF) and transforming growth factor beta (TGF beta). The second aim will be to elucidate the mechanisms that determine the peptidergic phenotype of denervated human and rat airway parasympathetic ganglia. The expressions of protachykinin gene products and their receptors will be studied by in situ hybridization, solution hybridization-nuclease protection assays, and immunohistochemistry in denervated rat lungs and xenografts prepared by implanting rat airways and human bronchi into subcutaneous tissue of immonodeficient mice. The resultant temporal profile of pre-protachykinin and neurokinin receptor expressions will be: 1. related pharmacologically to neurokinin contribution to bronchomotor tone, 2 evaluated after extended neurokinin receptor inhibition, and 3. contrasted to the expression of neurotrophins by denervated airway tissues and neurotrophin receptors by ganglion neurons. The information gained from this research will not only advance the current understanding of the biological function of airway nerves, but will also provide valuable insight into the pathogenesis of lung transplantation-induced bronchiolitis obliterans and other potential airway injuries cause by pharmacological or mechanical disruption of airway smooth muscle tone.